Energy impacts of recycling disassembly material in residential buildings Weijun Gao a,* , Takahiro Ariyama a , Toshio Ojima a , Alan Meier b a Advanced Research Institute for Science and Engineering, Waseda University Okubo3-4-1, 169-8555, Tokyo, Japan b Berkeley Lab LBNL), University of California, Berkeley, CA 94720 USA Received 24 February 2000; accepted 14 August 2000 Abstract In order to stop the global warmth due to the CO 2 concentration, the energy use should be decreased. The investment of building construction industry in Japan is about 20% of GDP. This fraction is much higher than in most developed countries. That results the Japanese building construction industry including residential use consumes about one third of all energy and resources of the entire industrial sectors. In order to save energy as well as resource, the recycle of the building materials should be urgent to be carried out. In this paper, we focus on the potential energy savings with a simple calculated method when the building materials or products are manufactured from recycled materials. We examined three kinds of residential buildings with different construction techniques and estimated the decreased amount of energy consumption and resources resulting from use of recycled materials. The results have shown for most building materials, the energy consumption needed to remake housing materials from recycled materials is lower than that to make new housing materials. The energy consumption of building materials in all case-study housing can be saved by at least 10%. At the same time, the resource, measured by mass of building materials kg) can be decreased by over 50%. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Residential building; Material recycle; Energy consumption; Japan 1. Introduction The investment of building construction industry in Japan is about 20% of GDP [1]. This fraction is much higher than in most developed countries. In the United States, for example, only 8.5% of investment goes to construction of buildings [1]. New homes constructed in Japan are about 12.6 homes/1000 persons in 1996, which is twice more than that 5.3 homes/1000 persons) in the United States. One explanation for this large fraction is the short lifetime of the average Japanese home and the more rapid turnover in the housing stock compared to that in North America because of high land cost and depreciation value of buildings. That results the Japanese building construction industry including residential use consumes about one third of all energy and resourcesoftheentireindustrialsectors[2].Thetrendbecame more pronounced in the 1990s when the energy required constructing a new building rose to nearly twice that required in the 1980s. The stream of waste from residential construc- tion projects rose in a similar manner. The wastes from the construction sector are about 200 ton/km area of the nation and 20 times higher than that 10.7 ton/km 2 ) in the United States [3]. Considering the size of the national land area of Japan, that is a terrible ®gure and means a lot of wastes are disposed into the narrower land area of Japan. Although techniques for the recycling of these materials are available, only about 50% of demolition waste was recycled in 1995. In Japan, the goal of waste management is becom- ing stricter and higher goals for recycling rates are being established. In Japan, 80% of demolition waste will have to be recycled next century [4]. The recycling of disassembled material of buildings and energy saving in making building products is one element of a broader Japanese policy to reduce environmental impacts of economic growth. This paper examines the impact of different construction tech- niques on the energy use of construction and operation, and the ability to eventually recycle materials from the demolished building. Recycling is widely assumed to be environmentally ben- e®cial, although the disassembly, collection, sorting and processing of materials into new products also entails sig- ni®cant environment impacts. In Japan, the technology for recycling the disassembled material of buildings has been widely studied. Sakai et al. [5] estimated the energy con- sumption of the production on the basis of the analysis of the inter-industry energy ¯ows. Noshiro et al. [6] examined the structural methods for recycling the materials from Energy and Buildings 33 2001) 553±562 * Corresponding author. Tel.: 81-3320-39450; fax: 81-5272-2598. E-mail address: weijun@mn.waseda.ac.jp W. Gao). 0378-7788/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII:S0378-778800)00096-7